The present invention relates to new compounds useful in assisting in the polymerization of monomers in a free radical polymerization that has living-type kinetics. Polymers made with the control agents and processes for polymerization are also included. In addition, some of the compounds themselves are novel.
The use and mechanism of control agents for free radical polymerization is now generally known, see for example WO98/01478, WO99/35177, WO99/31144, and WO98/58974, each of which is incorporated herein by reference. Despite this knowledge, no successful commercialization of a polymerization process has occurred with these agents. Thus the need for new agents, which lead to a commercializable process are needed.
In addition, the previously known control agents have limited uses. Although touted as universally useful, those of skill in the art appreciate that a particular control agent is particularly useful for the control of particular monomers and monomer mixtures. The polymerization conditions under which particular control agents are particularly useful are generally not well known. Thus, a need exists for a family of related control agents that can be easily synthesized and modified so that a control agent will be readily available for polymerizing desired monomers under commercially acceptable conditions, which include high conversion at the shortest possible reaction times and lower temperatures.
This invention solves these issues by providing control agents that can be easily modified for particular monomers and monomer mixtures. The control agents of the present invention contain at least one nitrogenxe2x80x94nitrogen bond, which allows for simpler modification of the electronic and steric nature of the control agents as compared to known control agents. These modified properties allow for improved conditions of the polymerization process and/or improved properties of the polymers obtained from the processes.
This invention provides control agents that are easy to prepare and economically useful on a commercial scale. In particular, the control agents of this invention have a nitrogenxe2x80x94nitrogen bond, which is believed to provide better chemical stability of the control agent together with a greater flexibility for chemical modification of said control agents, while giving control of a polymerization reaction that includes a free radical.
In general, the control agents of this invention have a Nxe2x80x94N bond covalently bonded to a thiocarbonyl moiety. In some embodiments the control agents can be characterized by the general formula: 
wherein D is S, Te or Se; R1 is generally any group that is sufficiently labile to be expelled as its free radical form; R2 and R3 are each independently selected from the group consisting of hydrogen, hydrocarbyl, substituted hydrocarbyl, heteroatom-containing hydrocarbyl, and substituted heteroatom-containing hydrocarbyl, and combinations thereof, and R4 is selected from the group consisting of hydrogen, hydrocarbyl, substituted hydrocarbyl, heteroatom-containing hydrocarbyl, and substituted heteroatom-containing hydrocarbyl, and combinations thereof, and optionally, R4 combines with R2 to form a ring structure, with said ring having from 3 to 50 non-hydrogen atoms. In some embodiments, R2 can form a ring structure with R1, as discussed herein.
Another aspect of this invention is directed toward multi-functional control agents, so that the control agents may occupy either a central portion of a polymer chain and/or two or more ends of a polymer. In those embodiments where the control agent occupies a central portion of the polymer backbone, the nitrogenxe2x80x94nitrogen bond provides the unique opportunity to degrade the polymer backbone into smaller pieces by external stimuli (e.g., heat, chemical reaction, irradiation, etc.). Such a process is unique as compared to known free radical polymerization and xe2x80x9clivingxe2x80x9d free radical polymerization techniques. In addition, some of the multi-functional control agents are cyclic, which provide the unique opportunity to prepare block copolymers with reduced processes steps. Furthermore, some multi-functional control agents allow for ring opening polymerizations, which heretofore have not found commercial applications in free radical polymerization.
Other aspects of this invention include certain of the control agents, which are novel compounds. Polymerization processes using all of the control agents of this invention and polymers that can be made with the control agents of this invention are additional aspects of this invention. In particular, the control agents of this invention provide living-type kinetics and as such allow for the preparation of desired products, including block polymers, star architectures, grafts and hyperbranched polymers.
Thus, it is an object of this invention to provide novel control agents for a living-type free radical polymerization process.
It is another object of this invention to provide novel compounds, which are useful as control agents in a free radical polymerization process.
It is a further object of this invention to provide a novel system for free radical polymerization of monomers that employs living-type kinetics.
It is still a further object of this invention to polymerize a variety of monomers under commercially acceptable conditions with a family of control agents.
It is yet a further object of this invention to make controlled architecture polymers with a polymerization process that employs a control agent.
It is further another object of this invention to provide multifunctional control agents that may occupy a central portion of a polymer chain allowing for the polymer chain to be degraded.
Further aspects and objects of this invention will be evident to those of skill in the art upon review of this specification.